WO-A1-85/05553 discloses bacterial cell surface proteins having fibronectin, fibrinogen, collagen, and/or laminin binding ability. Thereby it is shown that different bacteria have an ability to bind to fibronectin, fibrinogen, collagen and/or laminin. It is further shown that fibronectin binding protein from Staphylococcus aureus has a molecular weight of 165 kD, and/or 87 kD, whereby it is probable that the smaller protein is a part of the larger one.
Fibronectin is a large glycoprotein having a molecular weight of about 450 kD and having two similar subunits, which can have varying molecular sizes depending on a complex splicing pattern of the precursor mRNA. The protein is present in basement membranes, and connective tissue, but also in a soluble form in different body fluids, such as blood plasma (1). After the original discovery by Kuusela in 1978 that S. aureus binds to fibronectin (2) it has been shown that certain strains of other pathogenic bacteria, such as streptococci of different serological types (3), E. coli (4) and Salmonella (5) can bind to this protein (6).
Adhesion of pathogenic bacteria to surfaces is today a generally recognized concept in the discussions of wound pathogens using surface receptors to bind to different proteins on epithelium cell surfaces, in connective tissue matrix, and in wound crusts, such as e.g., fibronectin, fibrinogen, collagen and laminin. The problem is that these receptors are present in a relatively small amount on the bacterial cell surface, and that they are difficult to release. One feasible way in cases where the receptors consist of proteins is to clone the genes for the receptors in question to be able to prepare them in quantities which makes it considerably easier to study infections and the course of infections as well as proplylactic and therapeutic treatment of infections by wound pathogens.
Screening studies of different serological groups of streptococci, such as A, C, and G according to Lancefield (3) have shown that the strains tested can bind to different connective tissue proteins such as fibronectin, fibrinogen, collagen and laminin and different immunoglobulins (7,8) to a varying degree and with different specificity.
In order to further characterize fibronectin binding proteins from streptococci, particularly genes from Streptococcus dysgalactiae for such proteins have been cloned in E. coli. The fibronectin binding domains of these proteins have also been localized and properties and functions of proteins containing these domains will be discussed below.